Computer system

ABSTRACT

In order to enable an area of each logical volume to be expanded while continuously using the logical volume and to integrate separate logical volumes in a single continuous area, a storage has logical volume control means for controlling the construction of a logical volume, a logical volume number map in which logical volume construction information is described, and copy means for copying the logical volume. By allowing two or more inner logical numbers to be described per external logical number in the logical volume number map, improved flexibility in combining the logical volumes in the storage is achieved. By copying a plurality of separate logical volumes into a physical continuous area by the copy means, the logical volumes are integrated.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method of changing theconstruction of a logical volume area in a storage and, moreparticularly, a method of expanding a logical volume area.

[0002] Conventionally, as a method of expanding the capacity in astorage, an expansion method by adding a physical disk is known. Themethod will be described with reference to FIG. 15. Reference numeral100 denotes a storage and 101 indicates a physical disk area as acollection of physical disks. In the physical disk area 101, logicalvolumes called LU (Logical Units) designated by reference numerals 1011x (1011 a, 1011 b, . . . ) are constructed. In the case of expanding thecapacity of the storage, by adding a physical disk to the storage 100,as shown by a broken line, an added disk area 102 is generated. When thelogical volumes LU1 (1011 a) and LU2 (101 b) in the physical disk area101 become full, a new logical volume LU3 (101 c) can be generated inthe added disk area 102.

[0003] However, in the case of expanding the area of an internal logicalvolume already allocated to increase the usable capacity of the storage,a problem occurs. For example, in the case of enlarging the LU1 (1011 a)in FIG. 15, since the LU2 (101 b) immediately follows, the LU2 (101 b)has to be released. In order to enlarge the logical volume area in thestorage 100, the area has to be released once and allocation of thelogical volume area has to be newly defined. Consequently, an access toa logical volume has to be interrupted.

SUMMARY OF THE INVENTION

[0004] As described above, it is easy to increase the capacity of alogical volume area by adding a physical disk even during operation ofthe system. On the other hand, since the logical volumes are constructedin an inner continuous area, the area of each logical volume cannot beexpanded during operation of the system without newly adding a physicaldisk. In other words, to enlarge a logical volume area in a storage, thearea has to be released once and a logical volume area has to be newlydefined. A logical volume area cannot be therefore changed duringoperation of the system.

[0005] It is an object of the invention to enable the construction of alogical volume to be freely changed during operation of the system, forexample, to expand a logical volume area in a storage. Specifically, anobject of the invention is to provide a method of enabling the logicalvolume area to be expanded without releasing an existing logical volumearea and expanding the logical volume area without interrupting anaccess to an existing logical volume.

[0006] A computer system to which the invention is applied, therebyobtaining effects has, for example, at least one computer, a storage,and a control utility for instructing a construction change in a logicalvolume in the storage.

[0007] According to the invention, the storage has logical volumecontrol means for controlling the construction of the logical volume,and the logical volume control means is provided with a logical volumenumber map in which logical volume construction information isdescribed. By describing the constructions of the computer and logicalvolumes and the combination with logical volumes in the storage whichcan be used by the computer, a construction change in the logicalvolumes can be freely made. By copying a plurality of separate logicalvolumes into a physically continuous area so as to be integrated to asingle logical volume, management of the logical volume is facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a diagram showing the configuration of a computer systemaccording to a first embodiment of the invention.

[0009]FIG. 2 is a diagram showing an example of an LUN map of a storage1 in the first embodiment of the invention.

[0010]FIG. 3 shows a flowchart of a construction change in a logicalvolume LU in the first embodiment of the invention.

[0011]FIG. 4 is a diagram showing a state of the inner LUs in thephysical disk area in the first embodiment of the invention.

[0012]FIG. 5 is a diagram showing an example of an LUN map before aninner LU is changed in the first embodiment of the invention.

[0013]FIGS. 6A to 6C are diagrams showing examples of the LUN map afterchanging the inner LUs in the first embodiment of the invention.

[0014]FIG. 7 is a diagram showing a state of the inner LUs in thephysical disk area of FIG. 6A.

[0015]FIG. 8 is a diagram showing the configuration of a computer systemaccording to a second embodiment of the invention.

[0016]FIG. 9 shows a flowchart of a construction change in a logicalvolume LU in the second embodiment of the invention.

[0017]FIGS. 10A to 10C are diagrams each showing the state of inner LUsin a physical disk area corresponding to a construction change of thelogical volume LU according to the second embodiment of the invention.

[0018]FIG. 11 is a diagram showing an example of an LUN map before aninternal LU in the second embodiment of the invention is changed.

[0019]FIG. 12 is a diagram showing an example of an LUN map after theinternal LUs of the second embodiment of the invention are changed.

[0020]FIG. 13 shows a flowchart of a construction change in logicalvolumes LU of a third embodiment of the invention.

[0021]FIGS. 14A and 14B are diagrams each showing a state of an internalLU in a physical disk area corresponding to a construction change in thelogical volume LU according to the third embodiment of the invention.

[0022]FIG. 15 is a diagram showing an example of the configuration of astorage according to a conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The invention will be described hereinbelow by referring to thedrawings showing embodiments.

[0024] Embodiment I

[0025]FIG. 1 is a diagram showing the configuration of a computer systemaccording to a first embodiment. Shown in the diagram are computers 2 x(2 a, 2 b, . . ., 2 n), a storage 1 shared by all the computers 2 x, amanagement console 4 for managing the computer system, a fiber channelconnecting device 3 for connecting all the computers 2 x, storage 1, andmanagement console 4 with each other, fiber channels 5 x (5 a, 5 b, . .. , 5 n), a LAN (Local Area Network) 6 x (6 a, 6 b, . . . , 6 n) usedfor communications between the plurality of computers 2 x and themanagement console 4, and communication means 7 used for communicationsbetween the storage 1 and the management console 4.

[0026] Each of the computers 2 x has therein logical volume managementsoftware 21 x (21 a, 21 b, . . . , 21 n) called a file system FS orgenerally LVM, and a logical unit recognizing means 211 x (211 a, 211 b,. . . , 211 n) for recognizing a logical volume construction or the likeof the storage 1 and notifying the logical volume management software 21x of a change in the construction. The logical volume is a virtualvolume provided in the storage 1 and is a name defined in thespecification of an SCSI (Small Computer System Interface) as one ofprotocols of an interface connecting the computer 2 x and the storage 1.In the following, the logical volume may be also simply called an LU(Logical Unit). A number for identifying an LU will be called a logicalunit number (LUN).

[0027] The management console 4 has a control utility 41 used to displaythe LU construction in the storage 1, set an LU in the storage 1 by themanager of the system, and so on. The control utility 41 is disposed onthe management console 4 in this case but may be disposed in thecomputer 2 x or storage 1.

[0028] The storage 1 has therein a logical volume control means 11 forcontrolling the construction of a logical volume in the storage 1 andnotifying of logical volume construction information in response to arequest from the logical volume recognizing means 211 x in each computer2 x. Reference numeral 111 denotes a logical volume number map (LUN map)and is, as a component of the LU control means 11, a map showing logicalcorrespondence between the logical volume in the storage 1 and thelogical volume recognized by the computer 2 x. Reference numeral 12denotes a physical disk area which is a collection of physical disks. Inthe physical disk area 12, logical volumes 121 x (121 a, 121 b, . . . ,121 n) logically generated are provided.

[0029] The logical volume LU will be described. The LU is a logicalvolume seen from a computer 2 x (2 a, 2 b, . . . , 2 n) of the storage1. The computer recognizes an LU as a logical disk drive. The storage 1defines and internally constructs a plurality of LUs which will becalled internal logical volumes (internal LUs). In the storage 1, inorder to control the internal LUs, integers starting from zero areserially given to the internal LUs. The numbers will be called internallogical volume numbers (internal LUNs).

[0030] Generally, a computer searches a storage connected for an LU atthe time of booting the OS. There are the following two constraints tosearching methods, which are techniques of shortening a search time.

[0031] (a) To search the logical volume numbers LUN sequentially from 0.

[0032] (b) To stop searching when a certain number does not exist onassumption that the logical volume numbers LUN exist as serial numbers.

[0033] It is also assumed that the computer of the invention has suchcharacteristics. In such a case, when the internal logical volume numberLUN is assigned as it is to a computer, a computer to which a numberother than zero is assigned cannot detect the LU. Specifically, in eachof all the computers, it is assumed that the logical volume numbers LUNused by the computer start from zero. When the inner logical volumenumbers are directly assigned as the logical volume numbers LUN,consequently, for the computers to which numbers other than zero areassigned as the internal LUNs, it is equivalent that no logical volumeLU is assigned. Therefore, the inner logical volume numbers LUN startingfrom zero seen from the computer and which are serial numbers have to beassigned to each of all the computers.

[0034] In the invention, the storage 1 re-defines the internal LUs usedby a computer 2 x so that serial logical volume numbers starting from 0when seen from the computer 2 x are assigned to the internal LUs used bythe computer 2 x, thereby solving the problem. An LU recognized by eachcomputer 2 x will be called an outer logical volume (outer LU) and thenumber assigned to the outer LU will be called an outer logical volumenumber (outer LUN), so as to be distinguished from the inner LU andinner LUN, respectively. According to the invention, LUN combininginformation to define the relation between an outer LU and an inner LUis provided between the outer and inner LUs. By using the LUN combininginformation, the construction of combination between the outer and innerLUs can be changed. The corresponding relations among the outer LUN, LUNcombining information, and inner LUN are managed by the LUN map 111 inthe storage 1.

[0035]FIG. 2 shows an example of the LUN map 111 of the storage 1. Inthe LUN map 111, port number, target ID, outer LUN, LUN combininginformation, inner LUN, WWN, S_ID, and property are stored. The itemswill be described hereinbelow.

[0036] In the “port number”, the number of a fiber channel connectionport of the storage 1 is stored. In the embodiment, the number of portis assumed to be one, and “0” is stored.

[0037] The “target ID” is an identification of the storage 1 in theconnection interface between the computer 2 x and the storage 1. As inthe embodiment, when the connection interface between the computer 2 xand the storage 1 is a fiber channel, the only one D_ID (Destination ID)is assigned to each port. Since there is the item of the port number,the target ID may be omitted or D_ID determined at the time ofinitializing a fiber channel connection port may be stored. In the caseof the SCSI, the same port can have a plurality of IDs, so that thetarget ID to which each LUN belongs is stored. In the embodiment, it isassumed that the fiber channel is used, so that the column of the targetID is not used and zero is stored.

[0038] The outer LUN, LUN combining information, and inner LUN showcorresponding relations of each LUN. First, areas of physical disks inthe storage 1 are the logical volume areas having inner LUNs 0 to n−1and the logical volume areas having the inner LUN k. To each of theformer areas, “0” is assigned as the outer LUN. To each of the latterareas, “1” is assigned as the outer LUN. The LUN combining informationis information indicative of combining relation between the outer andinner LUNs. The left side of the LUN combining information indicates thetotal number of inner LUs assigned to the outer LU and the right side ofthe LUN combining information indicates the order of the inner LUs. Bothof the numbers are connected via a hyphen.

[0039] The “top LBA” indicates an address in the outer LU to which thetop address in each inner LU is assigned when it is seen from thecomputer 2 x. LBA (Logical Block Address) denotes an address in an LU,and the computer 2 x accesses data in the LU by using the address. Whenan outer LU is constructed by a single inner LU, “0” is assigned to thetop LBA. In the case where an outer LU is constructed by a plurality ofinner LUs due to a change in the construction of the LU, the top LBA isrewritten. This point will be concretely described when an example ofthe construction change of an LU will be described later.

[0040] “The number of blocks” indicates the number of logical blocks ineach inner LU, and the size of each inner LU can be known by the numberof blocks.

[0041] In the “WWN”, world wide name as information to specify eachcomputer 2 x is stored. In a port-login process to establish aconnection between a connection port of a fiber channel and a port, theWWN of each computer 2 x is notified to the storage 1. “S_ID” denotes IDinformation stored in a frame header of a fiber channel and is an ID ofa source (initiator) which generates a frame. S_ID is dynamicallyassigned at the time of initializing a fiber channel. Theabove-mentioned WWN is a value unconditionally set according to theconnection port of each fiber channel exchanged at the time ofinitialization. When WWN and S_ID are associated with each other,without checking the WWN each frame, only by checking S_ID, the computer2 x can be specified.

[0042] The “property” indicates the property of each LU. “Exclusive”denotes an LU exclusively used by a single computer 2 x. “Common”indicates an LU shared by a plurality of computers 2 x.

[0043] It is understood from the LUN map 111 shown in FIG. 2 that theinner LUs having the LUNs 0 to n−1 are exclusively assigned to thecomputers 2 a to 2 n, respectively. Although the inner LUNs are serialnumbers, all the outer LUNs are “0”. It is further known that an areahaving the inner LUN k is set for the common LUs. To the inner LU, theouter LUN of 1 is set. In the case of searching a storage at the time ofbooting the OS, by searching for 0 of the outer LUN and then 1, eachcomputer can know inner LUs which can be used by itself.

[0044] A construction change in the logical volume LU will now bedescribed by referring to the flowchart of FIG. 3.

[0045] The operator of the management console 4 sends an indication forLU construction change from the control utility 41. In the case ofexpanding an LU, the inner LUN of the LU to be expanded and an inner LUNof an LU newly coupled are designated. The indication is sent via thecommunication means 7 to the storage 1 (step 701).

[0046] The LU control means 11 in the storage 1 receives the indicationand determines whether the designated LU is correct or not (step 702).When the designated inner LU is not correct such that a not-existing LUNis designated, the inner LU to be newly combined has already assigned toanother computer 2 x, or the like, the LU control means 11 returns anerror signal to the control utility 41 and the routine is finished (step708). When the designated LU is correct, the LU control means 11rewrites the LUN map 111 in accordance with the indication (step 703).

[0047] The LU construction change is notified to the LU recognizingmeans 211 x in the computer 2 x by arbitrary one of the followingmethods; a method of transmitting the message from the LU control means11 to the LU recognizing means 211 x via the fiber channel 5 x, a methodof notifying the control utility 41 of the message by the LU controlmeans 11 in the storage 1 and notifying the message from the controlutility 41 to the LU recognizing means 211 x in the computer 2 x via theLAN 6 x, and a method of operating the computer 2 x directly by themanager to notify the LU recognizing means 211 x of the message (step704).

[0048] The LU recognizing means 211 x gets the changed LU size from theLU control means 11. The LU recognizing means 211 x may request the LUcontrol means 11 to present the construction information withoutreceiving the notification of the construction change. In this case, thenotification of the construction change (step 704) can be omitted (step705).

[0049] The LU recognizing means 211 x notifies the information of thechanged LUN and the size to the logical volume management software 21 x(FS or LVM) and the changed LU is enabled to be used on the computer 2 x(step 706).

[0050] As described above, while continuing an on-line access to anexisting LU, the construction change can be made reflected.

[0051] An example of the LU construction change will now be concretelypresented and rewriting of the LUN map 111 will be described in detail.As an example of the LU construction change, a case of expanding the LU0area in the computer 2 a will be taken. FIG. 4 shows a state of theinner LUs in the physical disk area 12. 120x (120 a to 120 c) denoteinner LUs. In the physical disk area 12, an LU0 area 120 a, an LU1 area120 b, and an LU2 area 120 c are continuously constructed. To simplifythe explanation, it is now assumed that the LU0 area 120 a is assignedto the computer 2 a, the LU1 area 120 b is assigned to the computer 2 b,and the LU2 area 120 c is of an inner LU which is not assigned to anycomputer. In the example, although the LU area 120 c is of the inner LUwhich is not assigned to any computer, since the LU1 area 120 b isformed continuously after the LU0 area 120 a, the LU0 area 120 a cannotbe expanded physically. In this state, the computer 2 a sees the LU0area 120 a as its logical volume, and the computer 2 b sees the LU1 area120 b as its logical volume.

[0052]FIG. 5 shows the LUN map 111 at this time. The inner LUND area isassigned to the computer 2 a (WWNa), the inner LUN1 area is assigned tothe computer 2 b 14 (WWNb), and the inner LUN2 area is blank (and theitems are not defined). When a request of expanding the LU of thecomputer 2 a is received, as described by referring to FIG. 3, the LUcontrol means 11 rewrites the LUN map 111 so that the inner LU2 120 cbecomes the inner LU of the computer 2 a on the basis of the instructionof the construction change sent from the control utility 41. FIG. 6Ashows the LUN map 111 rewritten in such a manner. As understood from theabove, the computer 2 a can recognize LUs having the inner LUNs 0 and 2as the LUs which can be used by itself. Since the inner LUN2 is usedcontinuously after the inner LUN0, it is assumed that a process startsfrom the number of blocks of the top LBA of the inner LUN 2. The processis performed by the LU control means 11. In association with theprocess, WWN, S_ID, and the like corresponding to those of the computer2 a are stored. In the case of accessing the LU from the computer 2 a,either the inner LU0 or LU2 to be accessed can be known from the topLBA.

[0053]FIG. 7 is a diagram for explaining the state of the inner LUs inthe physical disk area 12 rewritten as described above. As obviouslyunderstood in contrast to FIG. 4, although the inner LU120 x (120 a to120 c) are formed continuously in a manner similar to the above, an area122 indicated by an alternate long and short dash line functions as anLU of the computer 2 a. In this state, the computer 2 a sees the totalarea 122 of the LU0 area 120 a and the LU2 area 120 c as a logicalvolume which can be used by itself. The computer 2 b sees the LU1 area120 b as its logical volume.

[0054]FIGS. 6B and 6C show LUN maps 111 of other examples of the changedLU construction. FIG. 6B shows a state where, in addition to the logicalvolume obtained by adding the inner LU2 to the inner LU0 for thecomputer 2 a, the inner LU5 is further added. FIG. 6C shows a statewhere, in addition to the logical volume obtained by adding the innerLU5 to the inner LU0 of the computer 2 a, the inner LU2 is furtheradded. That is, FIGS. 6B and 6C show examples which are different fromeach other with respect to the order of adding the inner LUNs. Thedifference in the orders does not mean anything for the computer 2 a. Aslong as the LU control means 11 properly stores the top LBA andinformation such as WWN, S_ID, and the like associated with theconstruction change, in any of FIGS. 6B and 6C, the construction of thelogical volume having the block numbers of the total three inner LUs canbe used to execute the function of the computer of the LU control means11.

[0055] By virtually managing the LU areas as described above, theconstruction change such as expansion of an LU which cannot bephysically made out can be realized.

[0056] According to the embodiment, an effect of freely changing theconstruction of the logical volume areas in the storage is produced.According to the embodiment, another effect such that the logical volumearea can be expanded while continuing an access to an existing logicalvolume is produced. Further, according to the embodiment, theconstruction can be changed in the storage, an effect such that thelogical volume area can be expanded independent of the OS of thecomputer is produced.

[0057] Embodiment II

[0058]FIG. 8 is a diagram showing the configuration of a computer systemaccording to a second embodiment. The construction of the computersystem is the same as that of the first embodiment except for the pointthat a copy means 13 is added to the storage 1. The copy means 13 is ameans for copying an LU to another area.

[0059] An LU construction change will be described by using theflowchart of FIG. 9. The operator of the management console 4 sends anindication for LU construction change from the control utility 41. Inthe case of expanding an LU, the inner LUN of the LU to be expanded andan expansion size are designated. This indication is sent to the storage1 via the communication means 7 (step 801).

[0060] The LU control means 11 in the storage 1 receives the indicationand determines whether the total size of the size of the designatedinner LU and the expansion size can be assured from the free area or not(step 802).

[0061] When the area cannot be assured, the LU control means 11 sends anerror signal to the control utility 41, and the routine is finished(step 809).

[0062] When the area can be assured, the LU control means 11 assures thearea and sends a copy instruction for copy to the copy means 13 (step803). The copy means 13 which has received the copy instruction copiesthe designated LU. After finishing the copying of the LU, the copy means13 notifies a finish of copy to the LU control means 11 (step 804).

[0063] When the notification of copy end is received, the LU controlmeans 11 rewrites the LUN map 111 and assigns a newly generated LU tothe computer 2 x (step 805).

[0064] The processes in step 806 and subsequent steps are similar tothose in the first embodiment.

[0065] An LU construction change will now be concretely described. FIG.10 is a diagram for explaining an example of the construction change ofthe embodiment. FIG. 10A shows a state of the inner LUs before a change.In a manner similar to the case of FIG. 4, a case of expanding the LU0area of the computer 2 a will be taken as an example. In the physicaldisk area 12, the LU0 area 120 a and LUl area 120 b are continuouslyconstructed, the LU0 area 120 a is assigned to the computer 2 a, and theLU1 area 120 b is assigned to the computer 2 b. In this example, it isassumed that the area other than those areas is a free area. In thisexample as well, although there is a sufficient free area, the LU1 area120 b is formed continuously after the LU0 area 120 a, so that the LU0area 120 a cannot be physically expanded. In a manner similar to thefirst embodiment, the computer 2 a sees the LU0 area 120 a as itslogical volume, and the computer 2 b sees the LU1 area 120 b as itslogical volume.

[0066] A copying operation related to expansion of an LU will bedescribed first. When the operator of the management console 4 sends anindication for an LU construction change in which an inner LUN of the LUto be expanded and the expansion size are designated via the controlutility 41 to the LU control means 11, the LU control means 11 assuresan area of a new LU2 in a total size of the area size of the inner LUNof the LU to be expanded and the expansion area size in the free area123. When the area cannot be assured, an error signal is sent to thecontrol utility 41. The LU control means 11 instructs the copy means 13to copy the data of the LU0 120 a to the assured area LU2 120 d from thetop position of the area LU2 120 d. FIG. 10B is a diagram for explaininga copying state by the copy means 13. As shown by a broken line in thearea LU2 120 d, the data is copied from the LU0 120 a to the LU2 120 d.After copying all the data of the LU0 120 a to the LU2 120 d, the copymeans 13 notifies an end of the copy to the LU control means 11. FIG.10C shows a state of the inner LUs after completion of the copying. TheLU control means 11 which has received the copy end notificationrewrites the LUN map 111 and assigns the LU2 120 d to the computer 2 a.The LU0 120 a is not defined.

[0067]FIG. 11 shows an LUN map before updating, and FIG. 12 shows anupdated LUN map. It is understood that, in the LUN map before updating,the computer 2 a is assigned to the inner LUN 0. The computer 2 a isassigned to the inner LUN 2 in the updated LUN map. Moreover, the numberof blocks of the inner LUN 2 is larger than the initial number ofblocks. It is therefore understood that the area enlargement has beenrealized by using a new area. By using the copy means as describedabove, a new inner LU is generated while holding the original data inthe LU, so that the construction change such as LU expansion can berealized.

[0068] There is a case of accessing an LU from a computer during copyingoperation for the LU area change. In this case, when an access is a readaccess, it is sufficient to read data from the original LU area. If itis the write access, however, there is the possibility that a datadiscrepancy occurs unless data is written in both the original LU areaof the corresponding address and a new LU area. When the target of thewrite access is the original LU area on which the copying operation hasnot been completed by the copy means 13, there is no problem. When thetarget of the write access is the original LU area on which the copyingoperation has already been finished, even if data of the address isupdated, the new data is not read and copied to the new LU area.Consequently, if the copy end is notified in step 804, a datadiscrepancy occurs. When there is the possibility of occurrence of sucha data discrepancy, the LU control means 11 writes data to areas of boththe addresses during a period from step 802 to step 805. It is alsopossible to notify the address of the new area to the computer, andwrite the data to areas of both addresses by the computer.

[0069] As described above, by copying the data of the existing LU into anewly assured area, while utilizing the existing data, an LU areaexpansion or the like can be performed. Since one inner LU is assignedto one outer LU, the management is facilitated. According to theembodiment, the same effects as those of the first embodiment areobtained. Moreover, since the logical volume area is assigned to thephysically continuously area, an effect such that the management of thelogical volume is facilitated is produced.

[0070] Embodiment III

[0071] A third embodiment will be described. A computer system of thethird embodiment is the same as that in the second embodiment. The thirdembodiment is realized by a combination of virtual combining of logicalvolumes in the first embodiment and expansion by the copying means inthe second embodiment.

[0072] The LU construction change will be described by referring to theflowchart of FIG. 13.

[0073] The operator of the management console 4 sends an indication forLU construction change from the control utility 41. In the case ofexpanding the LU, all the inner LUNs assigned to the outer LU to beexpanded and an expansion size are designated. The instruction is sentvia the communication means 7 to the storage 1 (step 901).

[0074] The LU control means 11 in the storage 1 receives the instructionand determines whether the total size of the size of all the designatedinner LUs and the expansion size can be assured in the free area or not(step 902).

[0075] If the area can be assured, all the designated LUs are copied bycopy means and a new inner LU is generated. At this stage as well, ameasure to avoid a data discrepancy described in the second embodimentis taken. The subsequent process is similar to that in the secondembodiment (step 903).

[0076] When the area of the total size cannot be assured in the freearea, the LU control means 11 determines whether virtual combination ispossible or not. When the area of the expansion size can be assured, thevirtual combination can be performed (step 904).

[0077] When the virtual combination can be performed, the assured areaof the expansion size is virtually combined with the LU to be expanded(step 905). The following process is similar to that of the firstembodiment.

[0078] If the virtual combination is impossible, the LU control means 11returns an error signal to the control utility 41 and the routine isfinished (step 906).

[0079] An example of the result of the LU construction change accordingto the third embodiment will be described with reference to FIGS. 14Aand 14B. Reference numeral 12 denotes a physical disk area, andreference numerals 121 x (121 e to 121 h) indicate inner LUs. FIG. 14Ashows a state where the logical volumes are virtually combined accordingto the first embodiment, thereby constructing the outer LU 122. In thisstate, the computer sees the outer LU 122 as a single LU. In thestorage, however, it is known that the inner LU0 121 e and the inner LU2121 g are separated from each other. FIG. 14B shows a state where a newinner LU3 121 h having an area to be enlarged like the second embodimentis constructed. The data in the inner LU0 121 e and the inner LU2 121 gwhich are separated from each other is copied in a physically continuousarea and combined as a signal inner LU. In any of the cases, the LUN map111 is updated in correspondence with the case.

[0080] As described above, by combining the virtual combination oflogical volumes in the first embodiment and expansion by the copy meansin the second embodiment, a more flexible logical volume constructionchange can be realized. Particularly, since a plurality of separated LUscan be collected in a physically continuous area and integrated to asingle LU, the management of the inner LUs can be facilitated.

[0081] As understood also from the description of the embodiments, thelogical volume number map 111 of the invention does not have to have allthe port number, target ID, outer LUN, LUN combining information, innerLUN, top LBA, the number of blocks, WWN, S_ID, and property as in theembodiments. For example, as understood from FIG. 6, since the top LBAcan be calculated as a cumulative total of the numbers of blocks ofinner LUs including the immediately preceding LU, it is sufficient tocalculate the top LBA as necessary. In short, it is sufficient that thecombination of the outer LUN seen from the computer and the inner LUN ofthe storage is clearly defined, and the computer to which thecombination is used is known.

1. A computer system comprising: at least one computer; a storage havinga logical volume which can be used by the computer; and a controlutility for instructing a change in a logical volume of the storage,wherein said computer has logical volume recognizing means forrecognizing a construction change in the logical volume in said storage,said storage has logical volume control means for controlling theconstruction of the logical volume, and the logical volume control meanshas a logical volume number map describing logical volume constructioninformation.
 2. The computer system according to claim 1, wherein saidlogical volume number map includes: a logical volume number seen fromsaid computer; a logical volume number in said storage; and logicalvolume number combining information describing a combining relationbetween the logical volume number seen from the computer and the innerlogical volume number of said storage, according to an instruction fromsaid control utility, said logical volume control means describes a newcombination relation between the logical volume number seen from thecomputer and the inner logical volume number of the storage into thelogical volume number map with respect to an inner logical volume of thestorage, of which correspondence with the computer has not been defined,thereby changing the logical volume construction, and the constructionchange of the logical volume assigned to said computer is recognized bysaid logical volume recognizing means.
 3. The computer system accordingto claim 1, wherein the number of blocks indicative of the size of saidinner logical volume is described in said logical volume number map, andwhen a plurality of inner logical volumes are assigned, a cumulativetotal of the numbers of blocks of the inner logic volumes including theimmediately preceding the inner logic volume is used as the top addressof each inner logical volume.
 4. The computer system according to claim2, wherein the number of blocks indicative of the size of said innerlogical volume is described in said logical volume number map, and whena plurality of inner logical volumes are assigned, a cumulative total ofthe numbers of blocks of the inner logic volumes including immediatelypreceding inner logic volume is used as the top address of each innerlogical volume.
 5. A computer system comprising: at least one computer;a storage having a logical volume which can be used by said computer;and a control utility for instructing a change in a logical volumeconstruction of said storage, wherein said computer has logical volumerecognizing means for recognizing a construction change of the logicalvolume in said storage, said storage has logical volume control meansfor controlling the construction of the logical volume, and the logicalvolume control means has a logical volume number map and copy means forcopying said logical volume, and said logical volume control meanscompares a capacity of an undefined inner logical volume area and acapacity required by said control utility with each other by using dataof said logical volume number map in accordance with an instruction fromsaid control utility, and only in the case where the capacity of theundefined inner logic volume area is larger, a new inner logical volumeis defined in said undefined inner logical volume area, data recorded inthe area of the logical volume number designated by said control utilityis copied into said undefined inner logical volume area, and a new innerlogical volume number is set in a newly defined inner logical volumearea in response to completion of the copying.
 6. The computer systemaccording to claim 5, wherein in said logical volume number map, when anew inner logical volume number is set in the newly defined innerlogical volume area, an area corresponding to the logical volume numberdesignated by said control utility is changed to an inner logical volumewhose correspondence with said computer is not defined.
 7. The computersystem according to claim 5, wherein said logical volume control meansallows said computer to access said storage on both an areacorresponding to a logical volume number designated by said controlutility and an inner logical volume area newly defined while the copyingoperation by said copy means is performed.
 8. A computer systemcomprising: at least one computer; a storage having a logical volumewhich can be used by said computer; and a control utility forinstructing a change in a logical volume construction of said storage,wherein said computer has logical volume recognizing means forrecognizing a construction change of the logical volume in said storage,said storage has logical volume control means for controlling theconstruction of the logical volume, and the logical volume control meanshas a logical volume number map in which construction information oflogical volumes is described and copy means for copying said logicalvolumes, according to an instruction from said control utility, saidlogical volume control means compares a capacity of an undefined innerlogical volume area and a capacity required by said control utility witheach other by using data of said logical volume number map, in the casewhere the capacity of the undefined inner logic volume area is larger, anew inner logical volume is defined in said undefined inner logicalvolume area and data recorded in the area of the logical volume numberdesignated by said control utility is copied into said undefined innerlogical volume area, and a new inner logical volume number is set in anewly defined inner logical volume area in response to completion of thecopying, and in the case where the capacity of said undefined innerlogical volume area is insufficient, according to an instruction fromsaid control utility, assignment of a logical volume number which isdescribed in said logical volume number map and is seen from saidcomputer and an inner logical volume number of said storagecorresponding to the inner logical volume number seen from the computeris changed to thereby enable a plurality of inner logical volume numbersof said storage corresponding to the logical volume seen from saidcomputer to be assigned.
 9. The computer system according to claim 8,wherein said logical volume number map includes the logical volumenumber seen from said computer, the logical volume number in saidstorage, and logical volume number combining information describing acombining relation between the logical volume number seen from saidcomputer and the inner logical volume number of said storage, accordingto an instruction from said control utility, with respect to an innerlogical volume of the storage of which correspondence with the computeris undefined, said logic volume control means describes a new combiningrelation between the logical volume number seen from the computer andthe inner logical volume number in said storage into the logical volumenumber map, thereby changing the logical volume construction, and theconstruction change of the logical volume assigned to said computer isrecognized by said logical volume recognizing means.
 10. The computersystem according to claim 8, wherein the number of blocks indicative ofa size of said inner logical volume is described in said logical volumenumber map, and when a plurality of inner logical volumes are assigned,a cumulative total of the numbers of blocks of the inner logic volumesincluding the immediately preceding inner logic volume is used as thetop address of each inner logical volume.
 11. The computer systemaccording to claim 9, wherein the number of blocks indicative of a sizeof said inner logical volume is described in said logical volume numbermap, and when a plurality of inner logical volumes are assigned, acumulative total of the numbers of blocks of the inner logic volumesincluding the immediately preceding inner logic volume is used as thetop address of each inner logical volume.
 12. The computer systemaccording to claim 8, wherein in said logical volume number map, when anew inner logical volume number is set in the newly defined innerlogical volume area, an area corresponding to the logical volume numberdesignated by said control utility is changed to an inner logical volumewhose correspondence with said computer is not defined.
 13. The computersystem according to claim 8, wherein said logical volume control meansallows said computer to access said storage on both an areacorresponding to a logical volume number designated by said controlutility and an inner logical volume area newly defined.